1. Field of the Invention
The present invention relates to a television for displaying an image by adjusting a pedestal level (black level) of a video signal in a synchronization time of a synchronizing signal by an amount of adjustment according to an adjustment value for the pedestal level, and to an adjustment method for the same.
2. Description of the Prior Art
Televisions are conventionally provided with a video amplification-chroma circuit mainly comprising a chroma IC, a microcomputer IC, a video output circuit for generating signals of three primary colors, such as RGB signals (a red (R) signal, a green (G) signal and a blue (B) signal) or the like, a picture tube, a deflection circuit for generating a high-frequency signal and a drive current, a deflection coil, a high voltage circuit having a flyback transformer (FBT) for supplying the picture tube with high voltage, and the like. The video amplification-chroma circuit generates a sawtooth-like drive signal and a RGB color signal from a component video signal inputted thereto which consists of a luminance signal (Y) with a synchronizing signal component superimposed thereon, a red color-difference signal (V, Cr, or the like), and a blue color-difference signal (U, Cb, or the like).
The V signal and the U signal are provided with respective pedestal level adjustment values for adjustment of pedestal levels thereof which values are stored in a semiconductor memory. The video amplification-chroma circuit adjusts the pedestal level of each of the V and U signals by an amount of adjustment according to the corresponding adjustment value during a horizontal synchronization time of a horizontal synchronizing signal. This is because electric noise may get into the V and U signals from the FBT during the horizontal synchronization time, causing deviation in the pedestal levels of the V and U signals. More specifically, an operator in a television manufacturing plant makes efforts to connect a television to a computer, to perform an input operation of a pedestal level adjustment value into the computer so as to eliminate the deviation in the pedestal level during the horizontal synchronization time, and to write the pedestal level adjustment value in the chroma IC from the computer via an IIC bus of the television.
Such a technology has been hitherto known as disclosed in, for example, JP-A-2000-13805.
Particularly, making an effort to write the pedestal level adjustment value in the chroma IC as described above involves complex processing, which is time consuming.
It should be noted that the technology as disclosed in the above patent document cannot solve the above-mentioned problem because it involves allowing chromaticity of images of a plurality of input video signals to be adjusted by a common operation. This technology needs to take the trouble to demodulate and modulate the input video signal, leading to a complicated structured circuit.